Certain sports, such as football, rugby, American football, cricket, baseball, golf athletics, etc., require shoes of which the soles include projections. Such projections, which may be more or less aggressive: spikes, studs, serrations . . ., enable the player to move faster over loose or slippery surfaces (lawns, hard courts, carpets, etc.).
Said projections are subject to much wear. Consequently they must be either interchangeable, or wear-resistant and be integral with the outsole.
Whatever the solution chosen, the presence of the projections creates a feeling of discomfort in that, since the weight of the body is distributed over some of the projections only, the sole of the foot receives, by reaction, high pressures in those parts where said projections are situated. This causes painful feelings which can be overcome by producing the outsole in a very rigid material, yet this opposes the bending of the foot and makes the shoe considerably heavier.
It is therefore the object of the present invention to provide an outsole which no longer causes pains to the sole of the wearer's foot during sports, and which, in addition to comfort, exhibits many other advantageous properties, such as:
efficiency on loose, slippery, abrasive or other surfaces, PA1 rigidity and suppleness depending on the areas, PA1 resistance to abrasion, PA1 resistance to repeated bendings in all temperatures, PA1 dampening of shocks and vibrations, PA1 lightness PA1 easy bonding under the upper, PA1 low and competitive cost. PA1 in that stiffening plates in plastic material are provided with projections, projecting from their lower surface, and integrally molded, by their upper surface with the sole body in the instep area, PA1 in that a substantially elliptic aperture is provided in the sole body such that its major axis is situated on the bending axis of the outsole which corresponds to that of the foot in the metatarsophalangeal area, and that its center is situated a few millimeters, on the outside, from the middle of the width of the sole body taken on said bending axis, PA1 in that a dampening cushion in expanded plastic material is provided inside said aperture such that it projects under the sole body and emerges to form an inside covering on the latter, PA1 and in that two stiffening plates are substantially trapezoid-shaped and are placed on either side of the aperture, symmetrically with respect to the center of the latter.
Given that no material of natural or synthetic origin can, on its own, combine as many properties, it is necessary, for producing the outsole, to use several types of materials.
But there are only few materials which have sufficient affinity between them to be bonded directly together without the need for external agents such as adhesives. And moreover, the assembling of materials which are apparently incompatible risks to prove expensive.
Finally, most materials, with the exception of rubbers and elastomers, have not, in their compact form, the natural qualities of vibration phenomenon dampening. On the other hand, some materials, when in expanded form,acquire remarkable properties of dampening of shocks and other vibration phenomena.